It has been a while since I read it, but I my memory doesn't fail me, there were a few tribes that were different. And these land used to be part of a couple Empire, so the book does present several places, ruins for the GM to build upon to explore and it also give information about a few of the peripheral nations on both side (East and West) that interacts with it more regularly, so trade is a possibility.

I mean, I'd say there's a wealth of RL examples to pull from that could be dropped into the Hordelands to add more variety, since I think the area had a super-limited amount of canon materials? Like, the area represented by the Hordelands on Faerun runs from RL Siberia to modern central Europe (Hungary, at a minimum), and potential covers groups like the Bulgars, Huns, Magyars, Manchu/Jurchens, Mongols, Turks, Ugyhars, Tartars, Crimeans, etc etc.

I recently did some brainstorming with my father over a Hordelands-like area and there are definitely different directions one can go in to flavor various nomadic groups. Example: we created a halfling society for the Hordelands where the halflings roam set paths across the vast interior plains in wagon caravans (think a hobbit hole, but its a wagon) and they have large war dogs with riders for scouting, defense, and the like.

Plus, not *everything* has to be nomadic. In fact, isn't the adventure "trilogy" from 2nd Edition based around a permanent city found in the mountains somewhere? So you can have your Silk Road cities, your Kabuls, your Xanadus, and they'd be few and far enough between that there's still some variety.

So, my first real question is whether this is just idle curiosity, or interest in the area but you haven't read the book, or just generating traffic for the FR? If you're genuinely interested, I would absolutely encourage you to take a look at it, and peruse the book. It was available from WotC as a free download, but, now, apparently is on the DMsGuild for $9.99USD, or something like that. I don't know if the two differ in the way the maps are presented, or anything, but, <shrug>.
Another point to clarify: This IS NOT a book. It's a boxed set with two books, several maps, and a slew of handout card with lots of info on them.
But, to your questions:

So, I just wanna point out a minor nitpick here, just for sake of clarity, and to help others if they haven't read the books. The Horde supplement specifically only covers a pseudo-Mongolian setting.
Bedouins, Plains Indians of the Americas, Huns, and Scythians are all "nomadic horse-riding societies", but, this set only covers A culture of this type … the fantasy-Mongolian one.

Are there any nomadic tribes that have things about them that make them feel different?

There's all kinds of things about the tribes, locales, and stuff that make them unique. There's, like, 15, tribes, I think, that're each interesting in their own right and, while similar in culture, each has it's own identity and was written with the intent of making them distinct enough from the others. There's a bunch of languages in the region which are spoken variously by many of the tribes, and communication between each is a whole thing if one is not bilingual or have a translator.
But, the set covers countries and their cities and towns, too.
As far as other things, there's a glacier that's a breeding ground of white dragons, a temple oasis occupied by oni (demons), interesting permanent settlements (full-on cities), a valley of gnolls, Kwachow, or the City of Melons, which gains its nickname from the large, sweet melons raised there, and even the Griffon Mountains where inhabitants of the foothills make their living by searching out griffon nests and stealing and training the young birds. One lord often sends gifts of trained riding griffons to the kings and princes of other lands.

Other than raids on the Silk Road, what goes on in The Hordelands, where there is interaction with outsiders?

All I can really say is that there actually is a section of the first volume that covers how they view outsiders, and even the lowliest amongst the tribes are counted as higher than foreigners.

But, there's all kinds of things that go on there, and there's a lot of cultural information that covers customs, events, tensions, wars, trade, monsters, storyhooks, GM's notes, plots, and just all manner of things to use, if one were to want to use it directly, or as source material for something like the World of Greyhawks Wolf and Tiger Nomads cultures.

My favorite location within the Hoardlands, is Dhaztanar: Jewel of Semphar. But I love pseudo fantasy-based Arabian settings. And I am a real sucker for fantasy cities.

I especially liked one of the "encounters" that was on the cards that came with the boxed set; Bad Wine, it was a great way to introduce outside characters to the city and its customs and various laws.

So, my first real question is whether this is just idle curiosity, or interest in the area but you haven't read the book, or just generating traffic for the FR? If you're genuinely interested, I would absolutely encourage you to take a look at it, and peruse the book. It was available from WotC as a free download, but, now, apparently is on the DMsGuild for $9.99USD, or something like that. I don't know if the two differ in the way the maps are presented, or anything, but, <shrug>.
Another point to clarify: This IS NOT a book. It's a boxed set with two books, several maps, and a slew of handout card with lots of info on them.

The Horde is more than the boxed set.

There are three novels (which I've read).

And there is FR12 Horde Campaign which seems to be a Battlesystem sourcebook that covers the plot of the novels. I own that and I've looked through it, but - being a Battlesystem book - it pretty much focuses on setting up fights between the Tuigan Horde and various other factions (there are chapters for the War with Semphar, Conquest of Khazari, Invasion of Shou Lung, War with Thay and War in Rashemen).

There is also FRA1 Storm Riders, which I didn't originally realise was a product for The Horde. I've got a topic for that and it seems that the plot is based around the idea that The Horde is sweeping across the region. (I think they might be designed to fit with the Empires Trilogy of novels.)

That's an interesting aspect to the Endless Wastes, but it does make the natives sound like a bit of a one-trick pony culture, because it's used as a background theme for pretty much everything I've read or researched.

I am interested in the Hordelands (and have been since 2011) and I do have the freebie download from the old WotC website somewhere (I've been through several computers since I first went online). I've been waiting for The Horde to get converted to Print on Demand, so I can buy a dead-tree copy. I wish WotC would get on with passing the files over to DriveThru RPG.

Anyhoo the reason why I posted this topic is that I am specifically looking for other things to do in the Hordelands.

It has been a while since I read it, but I my memory doesn't fail me, there were a few tribes that were different. And these land used to be part of a couple Empire, so the book does present several places, ruins for the GM to build upon to explore and it also give information about a few of the peripheral nations on both side (East and West) that interacts with it more regularly, so trade is a possibility.

The Silk Road goes through the Endless Waste, so I guess there must be a number of places for caravans to stop along that route.

Trade would certainly be a thing. But would trade just be people passing through or would there be any homegrown trade?

I guess that the nomads of the steppe could trade horses and various animal products (like leather) to each other and the people nearby.

I mean, I'd say there's a wealth of RL examples to pull from that could be dropped into the Hordelands to add more variety, since I think the area had a super-limited amount of canon materials? Like, the area represented by the Hordelands on Faerun runs from RL Siberia to modern central Europe (Hungary, at a minimum), and potential covers groups like the Bulgars, Huns, Magyars, Manchu/Jurchens, Mongols, Turks, Ugyhars, Tartars, Crimeans, etc etc.

You're right. I get the impression that The Horde focuses on Mongol-like people. The Tuigan Horde is definitely a Mongol-like tribe, but I would like to see a bit more variety.

Not to mention that Toril is a magical world and would have non-human nomads, as well as some folks that could cast spells or make magic items.

I recently did some brainstorming with my father over a Hordelands-like area and there are definitely different directions one can go in to flavor various nomadic groups. Example: we created a halfling society for the Hordelands where the halflings roam set paths across the vast interior plains in wagon caravans (think a hobbit hole, but its a wagon) and they have large war dogs with riders for scouting, defense, and the like.

Mobile homes, instead of yurts would make some sort of difference to the culture. I guess you could "dock" different wagons together or install "bridges" between them, to create larger buildings. You could effectively have a mobile town.

Plus, not *everything* has to be nomadic. In fact, isn't the adventure "trilogy" from 2nd Edition based around a permanent city found in the mountains somewhere? So you can have your Silk Road cities, your Kabuls, your Xanadus, and they'd be few and far enough between that there's still some variety.

The map on page 5 of FR12 has some mountain ranges. They seem to work as the borders between some of the tribes. Presumably the tribes are able to defend against attacks through the mountain passes in the summer and the mountain regions close up in the winter.

The mountains would presumably be a good place to sneak in a dwarven or drow city...or something else that could threaten the people of the stepps (like an illithid city that raids for slaves to eat brains).

And there is FR12 Horde Campaign which seems to be a Battlesystem sourcebook that covers the plot of the novels. I own that and I've looked through it, but - being a Battlesystem book - it pretty much focuses on setting up fights between the Tuigan Horde and various other factions (there are chapters for the War with Semphar, Conquest of Khazari, Invasion of Shou Lung, War with Thay and War in Rashemen).

These 2 are indeed closely linked, and it's great to see what else are around the Waste and does give good plot ideas for a Horde campaign.

Aside from that, they could be trading with each other or merchant, raiding (each other, merchants, nearby nation), exploring the various ruins that dots the land, mage hunting eould be very "in character" of most horsemen too. It might need a bit of work, but there is potential for a full campaign.

There is also FRA1 Storm Riders, which I didn't originally realise was a product for The Horde. I've got a topic for that and it seems that the plot is based around the idea that The Horde is sweeping across the region. (I think they might be designed to fit with the Empires Trilogy of novels.)

The FRA1-3 Trilogy is an odd one. It is set in the East with the Horse Invasion in the background, it explore, peripheral kingdoms, ruins and past Kingdom and introduce elements of 1st ed Oriental Adventures to 2nd ed, but assumes players are Westerners. Although the Oriebral kits from the Complete Book of..., the Dragon article for the other kits: Bushi, Kensai, etc., the Complete Book of Ninjas and Scarlet Brotherhood (Greyhawk book, but has the monks properly converted to 2nd Ed would allow a full Oriental Adventure here. A good addition overall.

The Silk Road goes through the Endless Waste, so I guess there must be a number of places for caravans to stop along that route.

There are and the caravan itself could be it's own adventure (May be still idea from PF Jade Regent) an Middle Eastern/Indian like caravan, trading and defending versus the Horde and then oriental Adventures. Each tribe would have their own general view and approach to the caravan. Will they Raid, trade or be as likely to do both? Can the caravan give them an edge over the other tribe they are warring against.

I like to think of each tribe as a meta-character with it's own personality and goals, it helps with an organic flow of action/adventures.

Edit:
Oh and the various "Barbarian" or "horselord" kits from the "Complete Book of ..." serie would good kits for them as the Horde are the "Plain Barbarian" from Oriental Adventures.

The Horde is more than the boxed set.
..
I've been waiting for The Horde to get converted to Print on Demand ..

This kind of cracked me up.
I get what you're saying though. … that portion of the setting which is Mongolian Horde themed has more to it than just the boxed set. The Horde, by name, though, is only the boxed set. The other things have other names. But, yes, in what you mean, you're correct.

But, I couldn't help but chuckle a little when you said The Horde is more than a boxed set, then later literally said it again as the name of the boxed set, itself.

I recently did some brainstorming with my father over a Hordelands-like area and there are definitely different directions one can go in to flavor various nomadic groups. Example: we created a halfling society for the Hordelands where the halflings roam set paths across the vast interior plains in wagon caravans (think a hobbit hole, but its a wagon) and they have large war dogs with riders for scouting, defense, and the like.

Mobile homes, instead of yurts would make some sort of difference to the culture. I guess you could "dock" different wagons together or install "bridges" between them, to create larger buildings. You could effectively have a mobile town.

That works, yes. We looked more like "a hobbit hole from LOTR, but in a wagon", and figured that they would circle them together at night (think Conestogas in the American west), and link them with some kind of cloth walls or something to form a simple barrier. Each wagon would have a barrel and a system to collect rain water, a roof-top garden box, an under wagon box for refuse (used to grow mushrooms and cycle into other plant boxes after it turns into good dirt), window boxes, etc.

Our other big thing was dogs. These halflings would be dog riders, since it gives them an extra edge up in defending themselves (and makes them unique in the area) and in maintaining a small herd of cows or horses on their travels. The halflings are mostly peaceable, and most other tribes leave them alone because the halflings are the best source of fruits and vegetables for a lot of tribes (we envisioned that the halflings would have secret wild gardens scattered along their migration routes).

The map on page 5 of FR12 has some mountain ranges. They seem to work as the borders between some of the tribes. Presumably the tribes are able to defend against attacks through the mountain passes in the summer and the mountain regions close up in the winter.

The mountains would presumably be a good place to sneak in a dwarven or drow city...or something else that could threaten the people of the stepps (like an illithid city that raids for slaves to eat brains).

The mountains are a good use for this, yes. Some other things I've thought of over the years, in addition to expanding on the tribesmen to represent more than just Mongol cultures:

-Centaur tribes. These already exist, but can be given more emphasis...they aren't side notes, they are full-fledged tribes on par with human tribes.

-A mixed tribe. I have a single tribe that's half human and half centaur. Two small tribes on the brink of extinction made a pact for survival and have become one of the most dangerous tribes on the steppes because of it. Imagine all the advantages a solid cavalry archer has, and then replace the horse with a centaur mount. Two minds working in tandem, makes them doubly deadly.

-Orcs. Put orcs on horses, reflavor the orcs to be steppe nomads as desired. Its honestly a lifestyle that isn't all that different from what a lot of orcs elsewhere are already used to.

-Goblins. Goblins already ride worgs. I really like the thought that goblin tribes are nocturnal, finding semi-secluded spots to camp during the day and going out at night when most everyone else is camping. This makes raiding, say, animal herds (and the herders) easier for the goblins.

-Ogres. At first I was going to leave the ogres mountless, but then I remembered a fun little thing. Leucrotta. A small tribe of ogres (say, no more than a dozen?) mounted on leucrotta would be a formidable tribe on the steppes. Leucrotta are 7' tall in the 2e MC, which is at the upper end of RL draft horses. Make the body less stag-like and bulkier like a draft horse, and they'd be perfect mounts for ogres, to be honest. And an ogre tribe lead by an ogre mage who rides a greater leucrotta is just a bonus!

-Thri-kreen. The Horde book lists these as a common thing on the grassy plains parts of the Hordelands on Toril. I would steal judiciously from the Athasian thri-kreen to build a smaller empire somewhere out here. I imagine they are kept fairly small because any groups that stray beyond their borders are relatively easy pickings for any tribe that stumbles upon them, limiting the expansion of the thri-kreen. But this would definitely provide a "settled" kingdom in the plains.

-Spiders. So, any variation of 'bigger than large' spider can be found fairly commonly on the plains according to the boxed set. I imagine these are hunting spiders and not trapping spiders (so, imagine 5'+ tarantulas as opposed to web-spinners). There are also a lot of other giant insects, including millipedes, centipedes, antlions, etc. A small group of coordinated spiders hunting under the direction of an ettercap...and now I'm trying to work this out in my head. BRB.

-Giants. Stone giants. Maybe hill giants. Retool some giants to be steppes dwellers (desert giants from Al Qadim could be retooled for dry plains and deserts in the Hordelands perhaps?)

-Other Monsters. Dragons, behirs, cockatrices, chimaeras, manticores, hippogriffs, griffons, pegasi, anhkegs, leucrotta and a thousand other things provide a wealth of options. Some of the more intelligent monsters could provide settled locations (imagine ancient city ruins now home to a dragon, or a family of manticores).

-Camels. Not just in the deserts (though having desert regions with tribes more like the Ughyurs or Seljuk Turks is also good), but even on the plains. Most people forget that the Mongols had plentiful camels for riding and food, as did plenty of other tribes (such as the aforementioned Seljuk Turks). Camels are similar to horses, but have their own unique uses, which can provide some extra variance to a tribe.

-Other oddball things. I have one tribe that stays near a specific mountain, claiming its "sacred" to them. In reality, they aren't a tribe, but a nation-state built atop the mountain. They have a cavalry force formed from pegasi. They pretend to be a tribal horde to keep visitors away, but beware the poor bastard who attacks, only to find his opponents leaping into the air and assaulting his cavalry from above.

The official Hordelands actually has a lot of non-steppes terrain intermixed in the location, so there's plenty of locations to vary the standard take on hordes.